Re: [stable] [PATCH] devmem: check vmalloc address on kmem read/write

[Wu Fengguang <fengguang.wu@intel.com>]

On Thu, Feb 04, 2010 at 10:58:01AM +0800, KAMEZAWA Hiroyuki wrote:
> On Thu, 4 Feb 2010 10:42:02 +0800
> Wu Fengguang <fengguang.wu@intel.com> wrote:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > commit 325fda71d0badc1073dc59f12a948f24ff05796a upstream.
> > 
> > Otherwise vmalloc_to_page() will BUG().
> > 
> > This also makes the kmem read/write implementation aligned with mem(4):
> > "References to nonexistent locations cause errors to be returned." Here
> > we return -ENXIO (inspired by Hugh) if no bytes have been transfered
> > to/from user space, otherwise return partial read/write results.
> > 
> 
> Wu-san, I have additonal fix to this patch. Now, *ppos update is unstable..
> Could you make merged one ?
> Maybe this one makes the all behavior clearer.
> 
> ==
> This is a more fix for devmem-check-vmalloc-address-on-kmem-read-write.patch
> Now, the condition for updating *ppos is not good. (it's updated even if EFAULT
> occurs..). This fixes that.
> 
> 
> Reported-by: "Juha Leppanen" <juha_motorsportcom@luukku.com>

Sorry, can you elaborate the problem? How it break the application?

It looks that do_generic_file_read() also updates *ppos progressively,
no one complains about that.

Thanks,
Fengguang